The present invention relates to dinitro and fluorodinitroalkyl silicon compounds and more particularly to gem dinitrosubstituted silanes and polysiloxanes useful as energetic components of rocket propellants and explosives.
Nitro compounds were contained in the first recorded experiments with explosives as potassium nitrate in gunpowder. The important explosives TNT and nitrocellulose are, of course, also nitro compounds. Nitroglycerin is an aliphatic di-or tri-nitro compound. Gem, meaning twin, dinitro compounds have two nitro groups on the same carbon atom. They first became of interest after work on tetranitromethane was declassified after World War II. Tetranitromethane is sometimes considered an oxidizing agent rather than an explosive, although gem dinitro compounds are generally recognized as useful in the explosive arts.
Although not previously embodied in explosive compounds, the silicon-carbon bond is generally recognized as imparting favorable high temperature stability as well as low temperature fluid properties to organic compounds. Silicones are thermally and oxidatively stable and can retain flexibility or fluidity at very low temperatures. Silicones are characterized by their silicon-oxygen backbones. They commonly range from 24 monomer units in fluids up to 10,000 units in elastomers. Their properties are varied by varying the organic side chains on the silicon atom. For instance, methyl groups add thermal stability, phenyl groups impart oxidative stability, and vinyl groups are used for crosslinking. Although the chemistry of organosilicon compounds has been studied extensively, few examples of this class of compounds with nitro substituents are known. The hydrosilylations of 3-nitropropene, 4,4,-trinitrobutene and 4,4-dinitrobutene with trichlorosilane and methyldichlorosilane have been reported. U.S. Pat. No. 2,756,246 describes N.sub.2 O.sub.3 addition to allylsilanes, and U.S. Pat. No. 2,985,680 describes silver nitrate displacement of 3-iodopropyltriethoxysilane. The most commonly used methods of forming carbon-silicon bonds, the reaction of Grignard reagents and similar organometallics with silicon halides, and the reaction of elemental silicon with alkyl halides at high temperatures, are not compatible with nitro substituents. Polysiloxanes are usually obtained by the hydrolysis of silicon-halogen bonds, and these bonds are not stable to reaction conditions used for forming nitro silicones.